ced4568andClaude Sonnet 5
e007bcf000
Adds all 6 ROOT 02 modules (Linux system administration, storage & filesystems, the Networking Mental Model, Linux network inspection, DNS & HTTP, Linux troubleshooting) — 37 activities, each with a real lesson, demonstration/guided exercise, knowledge check, hands-on Lab, and reflection. The Networking Mental Model module (M3) gets deliberately extra depth per its "critical module" designation, with no lab by design — conceptual mastery via knowledge check and guided exercise, matching root-05-m00's own precedent. Adds 6 new hands-on Linux/networking scenarios plus 2 MCQs: linux-service-inspection (inspects the platform's own real nginx without touching it — a genuinely safe, real service-inspection target that avoids ever risking the Lab's own connectivity), linux-service-lifecycle (start/ verify/stop a fully controllable service), linux-storage-inspection, linux-network-inspection (ip/ss/getent/curl, each framed as answering one specific diagnostic question), linux-dns-http-diagnosis (a genuine DNS-resolves-but-wrong-port failure, diagnosed and fixed), and linux-troubleshooting-framework (a real missing-config-file failure, resolved via the RootNode Observe/Evidence/Hypothesis/Test/Repair/Validate/Prevent framework). All tested end-to-end via the real scenario-validation API, including negative tests confirming they fail when unsolved. Wires rootnode-linux-networking-assessment (2 required + 4 random-draw scenarios) using the existing Phase 3B assessment engine. Co-Authored-By: Claude Sonnet 5 <[email protected]>
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1.6 KiB
Guided Exercise: Diagnose From the Symptom Alone
This is a paper exercise — reason through each case using only the mental model, before any hands-on Lab work.
Your task
For each symptom, name which layer(s) it rules OUT, and which remain genuine suspects:
ping 8.8.8.8succeeds, butcurl https://example.comfails with "Could not resolve host."dig example.comreturns a correct-looking IP address, butcurl https://example.comtimes out with no response at all.curl http://internal-service:8080/returns "Connection refused," butcurl http://internal-service:9090/(a different port, same host) succeeds.
A worked shape to check yourself against
- Rules out: basic connectivity/routing to the internet (ping succeeded). Remaining suspect: DNS specifically — something is preventing name resolution even though raw IP connectivity works.
- Rules out: DNS (resolution clearly succeeded). Remaining suspects: routing/reachability to that specific IP, or a firewall silently dropping the connection — "no response at all" is the timeout signature, not the "actively rejected" signature.
- Rules out: DNS AND general reachability to that host (port 9090 worked). Remaining suspect: narrowed all the way down to "nothing is listening on port 8080 specifically" — the most precisely isolated diagnosis of the three.
Instructor Notes
Facilitation: Item 3 is the strongest example of "isolate one variable" reasoning (same host, different port) — worth highlighting explicitly as the gold-standard diagnostic pattern.
Approximate timing: 10-12 minutes live discussion; 8 minutes self-paced.